GREYWACKE or GRAUWACKE (a German word sig nifying a grey earthy rock), a term, formerly more generally used by British geologists than at the present day, for impure, com posite gritty rocks belonging to the Palaeozoic systems. They cor respond to the sandstones, grits and finer-grained conglomerates and breccias of the later periods. Attempts have been made to limit the term to those rocks formed from the disintegration of basic igneous and pyroclastic rocks, as distinct from arkose, sand stone, etc., which are formed from acid rocks. In view of the various denotations of the term greywacke, its use in geological literature seems now undesirable. The greywackes are mostly grey or brown dull-coloured sandy rocks containing a great var iety of minerals (such as quartz, felspar, calcite, iron oxides, gar net, epidote, etc.) and rock-fragments (felsite, chert, slate, gneiss, quartzite, etc.) . (P. G. H. B.) GRIBEAUVAL, JEAN BAPTISTE DE 7 89), French artillery general, was born at Amiens on Sept. 15, 1715. He entered the French royal artillery in 1732, and in 1752 be came captain of a company of miners. He was lent to the Aus trian army on the outbreak of the Seven Years' War, and served as a general officer of artillery. After his return to France he was made inspector of artillery, but he had to wait until 1776 before he became first inspector and was able to carry out the reforms in the artillery arm which are his chief title to fame. See ARTILLERY ; and for full details Gribeauval's own Table des con structions des principaux attirails de l'artillerie . . . de M. de Gribeauval, and the reglement for the French artillery issued in 1776.
See Hennebert, Gribeauval, lieutenant-general des armies du roy (Is96)